A foam distributor is part of a fixed piping fire suppression system capable of projecting a stream of fire-extinguishing compressed-air foam or other compressed-gas foam. In the art of firefighting, it is known to use foam produced from a solution of a foam concentrate in water. The volume of the solution is expanded by the addition of air and mechanical energy to form a bubble structure resembling shaving cream. The bubble suffocates and cools the fire and protects adjacent structures from exposure to radiant heat. Foam is known to be very effective on liquid fires, e.g. fuel, oil or other flammable chemicals.
One current approach to covering large floor areas is to use an oscillating nozzle to deliver the unfoamed solution. As the solution is substantially unfoamed when delivered, a more expensive agent is required and a higher concentration of the agent (e.g. in the neighbourhood of 3 percent) is required. A greater volume of the solvent and water are required to effectively cover the same area, in comparison with systems that agitate the solution to produce a thicker foam. This greater volume increases a cost per use, requires a greater supply of water and solvent (which can constitute considerable infrastructure and costs), and greatly increases the cost of disposing of the waste after a fire. Given that the delivery is across a semicircular arc, and that an array of these oscillating nozzles are required to cover the large surface area, the oscillating nozzle must be positioned only on the sides of the building. Moreover, these devices typically require a separate flow to provide the mechanical power to run the device. These oscillating devices are therefore inconveniently large, use 4-10 times more solution per unit coverage area, cannot cover 360 degrees and are unsuitable for other mounting configurations.
Foam can be generated using an air-aspirating nozzle, which entrains air into the solution and agitates the mixture producing bubbles of non-uniform size. With an aspirating system, the foam is formed at the nozzle using the energy of the solution stream. Unfortunately this foaming typically removes substantially all of the mechanical energy of the solution stream and consequently a second flow is typically required to supply mechanical energy needed to distribute the foam. The duplication of supply, and the coordination of the two systems increases an expense of the system and makes the system inherently less reliable.
Foam can also be generated by injecting air under pressure into the solution stream. The solution and air mixture are scrubbed by the hose (or pipe) to form a foam of uniform bubble size. The energy used in this system comes from the solution stream and the air injection system. This system produces a “compressed-air foam” (CAF) which is capable of delivering the foam with a greater force than a comparable aspirated system described above.
As is known in the art, compressed-air foam distributors are installed on ceilings and walls for fire-protection in a variety of applications, such as in warehouses and aircraft hangars. For example, in aircraft hangars, ceiling-mounted or wall-mounted foam distributors are poised to extinguish fires that might erupt if highly flammable jet fuel is accidentally ignited. The effectiveness of a distributor or a group of distributors to fight a fire depends on a number of factors, such as range or “reach”, i.e. the distributor's ability to project the foam an adequate distance, area coverage, i.e. the floor space it can cover, reliability, compactness, power efficiency, etc. Improving the effectiveness of a distributor provides superior fire-suppression, thus requiring fewer distributors to cover a given facility, which accordingly reduces building costs and saves space.
As is known in the art, coverage can be improved by rotating the nozzle of the distributor. A rotating nozzle is described by Applicant in Canadian Patent 2,131,109 (Crampton) entitled “Foam Nozzle”. This patent describes a foam nozzle having a stationary barrel and a rotary distributor with three tubular angled outlets. Other rotating nozzles are described in Applicant's U.S. Pat. Nos. 6,328,225 and 6,764,024 (Crampton) both of which are entitled “Rotary Foam Nozzle”. These patents describe an inverted-T-shaped rotary nozzle having a pair of differently sized orifices in the rotating barrel for distributing CAF in a circular pattern. Although these distributors provide good fire-suppression coverage, it would still be desirable to improve the effectiveness of the rotary foam distributor to further improve its ability to rapid suppress and control fires.
Furthermore, the distribution of compressed-air foam from small (prior-art) rotary nozzles cannot be practically scaled up in size to cover large areas, as scaling up in flow and size causes the rotational speed to increase to unacceptable levels and does not significantly increase the size of the coverage area. These prior-art nozzles are thus restricted to applications that do not require large areas of coverage. As is known by those of ordinary skill in the art, the problem in extinguishing flammable liquid pool fires in crowded aircraft hangars is delivering the CAF to the floor, past obstructions such as the wings or other vehicle bodies. Therefore, what is needed to cover large floor areas with CAF is a distributor that can deliver CAF to great radial distances with close to flat horizontal projection. It is further desirable to provide a distributor that has a low profile that permits installation in recessed horizontal settings, such as in a protected trough in a floor of the hangar.
Applicant's U.S. Pat. No. 6,764,024 discloses an impeller-driven delivery system that uses pressure of a CAF flow to drive an impeller, which is coupled by an internally mounted gear box reducer within a closed housing to revolve an output shaft that, in turn, drives a diffuser. The diffuser is made to revolve to distribute the CAF in a radial pattern.
Applicant has found that greatly improved transfer of energy to a rotor, and a significantly more compact assembly, can be achieved with a different configuration. This configuration further provides a more robust, simpler, impeller and transmission system that is better suited to surviving extreme thermal and shock testing required of such devices.
Therefore, it would also be highly desirable to provide a rotary foam nozzle that is compact, capable of covering a full 360 degrees, supplies CAF that does not require large water flow rates, does not require a secondary power supply, can be mounted in multiple configurations, and is robust.